(1) Field of the Invention
This invention relates to wheels and, more particularly, to resiliently cushioned wheels.
(2) Prior Art
Relatively hard, high capacity tires are often used in transport devices such as carts or industrial lift trucks used in production facilities of any number of products. While the use of such tires reduces rolling resistance and increases the load capacity of the cart, they produce a relatively hard ride for operator of the vehicle. Further, the shock loading imposed on cart components such as the axle and frame when the wheel goes over bumps or other irregular surfaces, tends to be relatively high and causes relatively fast wear of the wheel the cart components, and the floor.
Improved suspensions for in-plant dollies or other in-plant transportation vehicles have typically employed relatively expensive and elaborate spring suspension systems which can be likened to those of the automobile. Clearly, it would be desirable to reduce the wear on the cart wheels and on the floor without incurring substantial expense for an improved suspension. These are some of the problems this invention overcomes.
U.S. Pat. No. 3,072,169 issued to R. Hastings, Jr. on Jan. 8, 1963 and entitled "Resilient Wheel" teaches a wheel which has a shearing ring bonded between the wheel and the axle. The axle is not movable with respect to the axle mounting and the shear member is mounted between the wheel and the axle. As a result, increasing the size of the shear member necessitates the corresponding increase in the size of the wheel. Such an increase is undesirable because it adds weight and typically requires more substantial ball bearing for supporting the wheel. Again, all this adds to the cost of the suspension. Further, the patent only teaches a linear suspension wherein there is only provided the same amount of resilient resistance even as the wheel approaches the absolute limit of its travel. Thus, when the wheel does reach the limit of its travel, there may be an undesirably large shock loading.
U.S. Pat. No. 2,700,173 issued to L. D. Huffman on Jan. 25, 1955 and entitled "Cushioned Caster" teaches a relatively complex cushioning mechanism whereby the axle of the caster wheel is off set from a torsional cushioning member and swings with respect to the torsional cushioning member. The complexity of the cushioning mechanism results in a corresponding increase in cost. A U.S. Patent to Chesnut, No. 1,734,326 issued Nov. 5, 1929 and entitled "Caster Wheel" attempts to provide some of the cushioning through the tread and thus avoid the problem of having a hard tire altogether. However, such a solution also reduces the load capacity of the caster wheel. U.S. Pat. No. 2,669,448 issued to W. W. Cushman on Feb. 16, 1964 and U.S. Pat. No. 629,229 issued to C. Ballin on July 18, 1899 teach suspension systems including rubber balls which are required to twist and turn as the wheel turns with respect to the wheel mounting. Again, a relatively simple and less expensive solution would be desirable.